OTU classification and marker correlation
After sequencing, processing, and filtering of short-read (Illumina) reads, we found a total of 10,745 OTUs, of which 2,212 (20%) were identified as fungi for the 18S dataset. For COI we found a total of 6,227 OTUs, of which 2,161 (35%) were fungal. For the long-read (PacBio) reads of ITS, we obtained a total of 3,711 OTUs, of which 3,039 (82%) were fungal. The majority of the fungal OTUs were found to belong to the phylum Ascomycota, followed by Basidiomycota (Fig. 2). The 18S dataset was found to contain a higher proportion of non-Dikarya (Ascomycota plus Basidiomycota) than did the other datasets (Fig. 2). All the following results are based only on OTUs classified as Fungi.
The Effective number of OTU showed a weak correlation across datasets, with COI being more correlated with 18S (r = 0.36). The ITS was non-correlated with either 18S (r = -0.08) or COI (r = -0.02). The Mantel tests showed a significant (p = 0.001) correlation in all matrices of similarity, with the strongest correlation between 18S and COI (r = 0.52) and a weaker correlation with the ITS datasets (ITS and COI r = 0.30, ITS and 18S r = 0.17).